Visbreaking of reduced crude in the presence of light catalytic cycle stock



Aug- 18, 1959 H. BEUTHER E E -vIsBREAKING oF REDUCED CRUDE 1N THEPRESENCE OF' LIGHT CATALYTIC CYCLE STOCK Filed March 9, 1955 2,900,327.Patented Aug. 1s, 1959 ice VPaul Siecke, and Harold Beuther, filedDecember 20, 1951. 2 900 327 This invention provides a process in which'a better dis- 'VISEREAIQNG yon REDUCED CRUDE 1N THE PRESENCE or LrorrrCATALYTIC CYCLE sToCK assigner to Gulf Research & Development Company,

Pittsburgh, Pa., a corporation of Delaware H l, Y tions comparable tothose used for vis-breaking-'the'v'ery Application March 9, 1953,'Serial N0# 341,126 deeply reduced residues from vacuum stills mentionedEV5 Clainm (ci. 208 106) above. The yield of gasoline from the heatingand crack'- Y ing'of the mixtureis'markedly increased over that ob` l"tained when, for example, the catalytic cycle voil and the'` 'ThSiHVeIltOn relates '0.21l thermal Conversion PrOCeSS v15' residue areseparatelycracked under comparablecondiforthethermal conversion of'petroleurnfractiona and xjmore particularly to a process in whichcatalytic cycle i stocks and very heavy Vpetroleum residues areconverted" @to more volatile and valuable productsY by rthermalconjversion4V` I p, YInthe processing Iof petroleum crude oils, thecrude 1s tribution of the products obtained from petroleum crudes isobtained andparticularly one 'in which the yield of gasoline isincreased. According to this invention, alight catalytic cycle oil ismixed with avery heavy residue'from crude petroleum whichv has beendeeply reduced by vacuum distillation, and the"` mixture is"A heated andthermally cracked in furnace coi-lsA at severe cracking conditions."Moreover, the 'mixture may be cracked -at even more severe conditionsthan the very heavy residue alone withoutY excessive coke formation.

The single gure of the drawings isa diagrammatic representation of a owsheet of the process of this invention. Valves, meters, pumps,condensers, reux lines and j -r tutordinarily first passed nthrough adistillationc'olumn at" {tisubstantially atmospheric pressure in Iwhichgas and i other control 'equipment have been omitted from the drawingfor Simplification.

1 gasoline are removedas overhead products, naphtha and Referring to thedrawings, the feed stock, Vwhich .ordi- Y perhapsfahlight gasoil aretaken off as side streams, and' Y Y i the heavierfractions aredischarged as bottornsfrom the u 1` tower. lfhebottoms from theatmospheric tower are then j passed through avacuuin distillation towerin which a Ypheavy, gas -oil is taken overhead and a heavy residualfrac- 10 into an atmospheric distillation tower 12 from which gas istaken off Voverheadthrough line 14, and side. streams of gasoline,naphtha and light gas oil may be withdrawn Q -zgtion isnobtained fromthe bottom of' the vacuum tower.

l tdesirable crudes, hasforced renners to make deeper and i, I -having arelativ ely high content lofaromatics isproducedA' i through' side toweroutlets 16, 18 and 20, respectively. The bottoms from the atmospherictower `12 are with- ""dra`wn through line 22 and passed into a vacuumdistil- 'lation' tower 24 in which a Very deep cut is made to produce anexceptionally heavy petroleumtresidue as bot- 35 toms. A heavy gas oilis withdrawn at the top of the tower 24 through line 26 and passedto'apparatus, not shown, for further processing, such as vbycatalyticcracking. A very heavy residual fraction is withdrawn from the bottom oftower 24 through line 28. It will be appreciated that the atmospherictower 12 and vacuum tower i 24 are provided with the usual refluxequipment and other apparatus necessary for control of the operation ofthe towers'.V If necessary, 'a heater (not shown) may be used betweentheatmospheric and vacuum tower to supply the heat necessary for thedeep vacuum reduction of the The large and *steadily increasing demandsfor the more 1 volatile petroleum products, notably gasoline anddistillslate fuel oils, and-the necessity of processing heavier, less pdeeper cuts into the crpde. g p p M Y Y, Gas oils obtained as:distillates from the atmospheric v and vacuum distillation towers aregenerally cracked by either thermalv or catalytic processes tofor'rrrgasoline.4 I T *In catalytic cracking processes, a veryrefractory cycle oil aloggwith the gasoline. nAttempts to crack thecycle oils further, either catalytically or thermally, 'have generally ibeen unsatisfactory. In catalytic processes, large amounts "j f (ofkcarbon are deposited onY the catalyst lowconverv .sions -zto gasolineare obtained. In thermal processes,""

wery vsevere cracking conditions, together with very h igh recycleratios, Vvare `requiredto Vobtain a' satisfactory `cenversion togasoline. yOften recycle ratios as highas4 parts of recycle'to L1 .partof fresh feed are employed, rwith a consequent serious reduction in thecapacity of the ther'` mal cracking unit. Because of the difficulty incracking vthe catalytic cycle oil further, that stock is largely used toVcutpthe viscosity of heavy .fuel oils to meet specifications Yandjblendedlwith:virginfuels toformY furnace oil. Both of `these usesofthe catalytic cycle oil,` and particularly p its usetocut theviscosity-Mofheavy fuel, oils, seriously l Ydecrease the'preturn tronithe catalytic Vcycle'oil 'as com--V`-` bottoms from the atmospherictower 12.

The extent ofthe reduction of the crude required to produce a chargestock suitable for use in the process of this invention will depend inpart 4upon the nature of the crude. In some instances, 4for example,where the crude is of a paraiiin base, the residue withdrawn throughline 28 may be only approximately 5% of the crude.

` With other crudes, such as a West Texas crude, the

pared with what might be obtained if the catalytic cycle oil couldsatisfactorily be convrtedto gasoline.

Residual stocks `from atmospheric distillation towers y l havecustomarily been subjected to a vis-breaking thermal "residue withdrawnfrom the bottom of the distillation tower 24 may constituteapproximately 10% of the crude. In general the heavier the crude, thelarger the percent of the total crude'that may be treated satiscrackingoperation which is essentially a mild cracking operationat temperaturesusually in the range of 825 F.' to 900 F. More' severecrackingconditions are not i Y possibleA because of excessive coke formation.`Recently,

it has been found that, contrary to expectations, residual `stocks muchheavier than these from atmospheric distilla tion, towers, may bevis-broken under vmore severe condi- 950,:o F., without excessive cokeformation.y That discov- A vtions, such astemperatures ofapproximately900 F. to

`factorily accordingrv to this invention. Residues .from certain heavycrudes such as those from Kuwait and "Mississippi may constitute asmuchas 20% and 30% 'of the crude, respectively.

It has been found that the residual fractions which may be successfullycracked according to this invention are those having a carbon ery-is thesubject matter of Application Serial'No; 262,566 70' IlOW US. Patent N0.2,762,754 Of William C. Olltt,

residue number of at least 18, a gravity in A.P.I. below 10 and an SUSviscosity at 210 F. of at least 6,000. The initial boiling point of theresidual fractions will generally be from 900 to 950 F., lbut willdepend in part on the fractionating eiciency of the vacuum tower 24.

According to this invention, thel residue 'from the bottom of tower 24is mixed with a light catalytic cycle oil introduced into line 28through a line 30. The light catalytic cycle oil may be obtained fromany of the wellknown catalytic cracking processes such as the Houdryfixed bed process, moving bed processes, or iiuid catalytic crackingprocesses. The boiling range of the light catalytic cycle stock willordinarily be within the range of 400 F. to 650 F., and preferablywithin the range of 400 to 600 F. It will be appreciated that anysuitable method of mixing the two fractions may be employed, and that amixture of the residue with the light catalytic cycle oil may be storedin suitable tanks and charged directly to the furnace, rather thanmixing the two fractions in the line Z8. The ratio of catalytic cycleoil to the residue may range from approximately 2 to 1, to 1 to 6.

Preferably, in the operation of the process of this invention, it willbe desirable to recycle fractions of the cracked product boiling abovethe gasoline range, as illustrated in the drawings. The recycle oil isintroduced into line 28 from line 32 for admixture with the lightcatalytic cycle oil and the residue prior to heating in the furnace 34.

The mixing of the light catalytic cycle oil with the residue from thevacuum tower 24 permits the use of more severe cracking conditions inthe furnace 34 than is possible in the usual visbreaking operationwithout the formation of the excessive coke which limits the crackingconditions in conventional visbreaking processes. For example, the shorttime conversion process of this invention will ordinarily beaccomplished with a furnace outlet temperature in the range of about 900F. to 1000 F., and preferably from approximately 950 F. to 1000 F. Theupper temperature limit will be determined in part by the heating curveof the furnace. If extremely high heating rates are possible,temperatures above 1000 F. may be used, in some instances, Withoutexcessive coke formation. The pressure `is not as important as thetemperature in controlling the reaction rate and severity of cracking. Apressure in the range of 50 to volume above 750 F. will be from about0.020 to 0.035 cubic lfeet per barrel per day. ln the preferred form ofthe invention illustrated in the flow sheet, the mixture of the lightcatalytic cycle oil, recycle oil, and the residue is quenchedimmediately after its discharge from the furnace outlet 'by means of astream of quenching oil introduced through line 36.

The cracked products from the furnace 32 are discharged through line 38into a separator 40 from which heavy fuel oil is withdrawn as a bottomsproduct through a line 42 and the more volatile products are withdrawnoverhead through a line 44. The conditions in the separator arecontrolled to regulate the initial point of the fuel oil. In thismanner, the end point of the recycle oil is also regulated, ordinarilyto form a recycle oil having a boiling range of approximately 400 to 600F.

The overhead product from the separator 40 is delivered through a line44 into a fractionating tower 46 which separates the more volatilecompounds from the y 400 to 600 recycle oil withdrawn from tower 46through line 32 for recycling through the furnace 34. The overheadproducts from tower 46 are delivered through a line 48 into a stabilizer50 from which gases are withdrawn as an overhead product through line52. Gasoline is taken from stabilizer S as a side product through lineS4, and 400 F. end point naphtha is withdrawn as bottoms through rline56. The lfractionator and stabilizer illustrated are conventional andshown only to complete the disclosure. Clearly, other fractionating andstabilization apparatus and procedures may be employed without departingfrom this invention.

It has been found that the process of this invention gives an improvedyield of gasoline particularly as compared with processes in which thelight catalytic cycle oil and heavy reduced crude are separatelycracked. In addition,`there is apparently less condensation to form inthe tubes of the furnace and, as a result, increases the 1000 p.s.i.gauge will ordinarily be used. The coil velocity in the tubes to sweepany coke whichrmay be formed from the coils.

The following examples illustrate theimproved opera` tions made possibleby this invention:

EXAMPLE 1 A West Texas crude oil was reduced in an atmospheric andvacuum distillation process of the type described to form a residualproduct constituting 9.9% of the crude. A light catalytic cycle stockboiling in the range of approximately 436 F. to 616 F. was added to theresidue, in such proportions that the reduced crude constiuted 72% ofthe mixture and the catalytic cycle stock the remainder, to form a totalcharge. The charge Was cracked in a coil at a maximum temperature of 950F. and a pressure of 400 p.s.i.g. in a short period cracking operation.The cracked products were fractionated to produce a 10 lb. Reid vaporpressure, 400 F. end point gasoline and a specification fuel oil. 'Ihefraction boiling between the end point of the gasoline and the initialboiling point of the specification fuel oil was recycled to extinction.The recycle oil amounted to 112% of the total charge.

EXAMPLE 2 The residue constituting 9.9% of a West Texas crude employedin Example 1 was cracked in a single pass conversion without theaddition of catalytic cycle stock. The single pass conversion lwasconducted in a coil at a maximum temperature of 950 F., and pressure of200 p.s.i.g., and the cracked products were fractionated to produce a 101b. Reid vapor pressure, 400 F. end point, gasoline, and a specicationfuel oil, as in Example 1.

EXAMPLE 3 A residue from vacuum distillation constituting 17.7% ofKuwait crude was mixed with a light catalytic cycle stock similar tothat employed in Example l in proportions of 68% reduced crude and 32%catalytic cycle stock to form a total charge. The charge was cracked ata maximum temperature of 950 F. and a coil outlet pressure of 400 p.s.i.gauge. The cracked products were separated into 10 1b. Reid vaporpressure, 400 F. end point, gasoline, and specification fuel oil. Thefraction boiling between the end point of the 400 F. gasoline and theinitial boiling point of the specication fuel oil was recycled toextinction. The recycle oil amounted to 111% of the total charge.

EXAMPLE 4 A residue constituting 17.7% of a Kuwait crude was cracked ina single pass operation without the addition of catalytic cycle stock.The maximum temperature of the cracking operation was 955 F., and apressure of 200 p.s.i.g. was employed.

In each of Examples 1 through 4, the time of cracking was substantiallythe same, as indicated by the coil volunie above .750 F. ofapproximately 0.02 cubic feet per barrel of throughput per day. 'I'heresults of the operations in Examples l through 4 are illustrated in thefollowing Table I:

Table I i Exain- Exam- Exam- Example 1 ple 2 ple 3 ple 4 Yallld of 10RVP 400 F. E.P. gasoe: Percent by vol. of total charge... 27.8 12. 432.5 18. 4 Yields: Percent by vol. of crudey 10 RVP 400 F. El".gasoline.-- 3.8 1.2 8. 4 3. 3 Fuel oil 10.8 11.5 18. 7 20. 2 Catalyticcycle stock requirement 4. 7 2. 7 l). 8 5. 4 Charge 3.8 0.0 8. 0.0Cutting 011 o. 9l 2. 7 1. 3 5. 4

If the light catalytic cycle stock added to the residue in Examples 1`and 3 is cracked separately to extinction in a recycle operation atconditions corresponding to the severity of Examples 1 and 3, and theresultant products combined with the products from Examples 2 and 4, theyields of gasoline and fuel oil obtained by cracking the fractionsseparately are obtained. A comparison of the yields of gasoline and fueloil obtained by processing of the combined heavy residues and lightcatalytic cycle stock according to this invention with yields obtainedby processing of the stock separately is set lforth in Table II.

p The separate cracking of `cycle stock and the residue of Example 2 isreported as Example 5 and of cycle stock and the residue of Example 4,as Example 6.

Table II Exam- Exam- Exam- Example 1 ple 5 ple 3 ple 6 Yields: Percentby Vol. of Total Charge- 10 RVPAOOD F. E.P. Gasoline--- 27.8 20.4 32. 525.3 Fuel Oil 78. 3 8l. 2 71.4 72. 9

EXAMPLE 5 A West Texas crude was reduced by successive atmospheric andvacuum `distillation steps to form a residue constituting 9.9% of theoriginal crude. A total charge was prepared by blending the residue witha light catalytic cycle stock having a boiling range of approximately400 F. to 600 F. in proportions of 3 parts by volume of residue to 1part by volume of cycle stock. The total charge was mixed with recycleoil and cracked in a furnace coil at a maximum temperature of 965 F. anda pressure of 400 p.s.i.g. The recycle oil consisted of the fraction ofcracked products boiling between the end point of the gasoline (400 F.)and the initial boiling point of the specification fuel oil. The recycleoil amounted to approximately 128% of the volume of the total charge.The results of the conversion are illustrated in Table III:

Furnace pressure 400 p.s.i.g.

Furnace coil volume above 750?. 0.02 cu. -ft/bisl. f

1. A process for the thermal conversion of petroleum hydrocarbonscomprising vacuum distilling a petroleum oil to form a Iheavy residue asa bottoms product having a gravity in API of less than 10, Conradsoncarbon residue number of at least 18, and an SUS viscosity at 210 F. ofat least 6000, mixing the residue with a light catalytic cycle oilhaving a boiling range of approximately 400650 F. to form a mixturehaving a ratio of residue to light catalytic cycle oil ranging from 1:2to 6:1, heating the mixture to .a temperature of 900 to 1000 F. in ashort period to crack residue and light catalytic cycle oil in themixture, separating the cracked products into fuel oil and a vaporphase, fractionating the vapor phase to produce gasoline and a recycleoil having a higher boiling range than gasoline as separate fractions,and returning recycle oil to the mixture for heating to crackingtemperatures.

2. A process for the thermal conversion of a heavy residue from thevacuum distillation of a petroleum oil, said residue having `a gravityin API of less than 10, a Conradson carbon residue number of at least 18and an SUS viscosity at 210 F. of at least 6,000, comprising mixing theresidue with a light catalytic cycle oil boiling in the range ofapproximately 400-650 F. to` form a -mixture having a ratio of residueto light catalytic cycle oil ranging from 1:2 to 6:1, rapidly heatingthe mixture to a temperature of 950-1000 F. in a coil having a volumeabove 750 F. less than about 0.035 cubic feet per barrel of throughputper day to crack the mixture, the time at the high temperature causingcracking of hydrocarbons of both the residue and light catalytic cycleoil, separating the cracked products into a liquid phase and a vaporphase, fractionating the vapor phase to produce gasoline and a recycleoil having a higher boiling range than gasoline as separate fractions,`and returning recycle oil to the mixture for heating to crackingtemperatures.

3. A process for the thermal conversion of a heavy residue from thevacuum distillation of a petroleum oil, said residue having a `gravitingin API of less than 10, a Conradson carbon residue number of. at least18, and an SUS viscosity `at 210 F. of at least 6,000, comprising mixingthe residue with a light catalytic cycle oil having a boiling range ofapproximately 400-650 F., in a ratio of residue to light catalytic cycleoil range from 1:2 to 6:1, rapidly heating the resulting mixture to atemperature of 950-1000 F. in a coil having a volume above 750 F. notexceeding 0.035 cubic feet per barrel of throughput per 'day to crackresidue and light catalytic cycle oil in the mixture, quenching theheated mixture, separating the cracked products into a fuel oil and avapor phase, and -fractionating the vapor phase to separate a gasolinefraction.

4. A process for the thermal conversion of petroleum hydrocarbonscomprising vacuum distilling a crude oil to form a heavy residue as aibottoms product having a gravity in API less than 10, a Conradsoncarbon residue number of at least 18, and a SUS viscosity at 210 F. ofat `least 6,000, mixing the residue with a light catalytic cycle oilboiling in the range of approximately 40G-650 F. to for-m a mixturehaving a ratio of residue to light catalytic cycle oil .ranging fromabout 1:2 to 6:1, heating the mixture to 'a' temperature of 900l000 F;to crack residue `and light catalyticV cycle 'oil in the mixture, andseparating the cracked products into a cracked residual oil and crackeddistillate fractions.

5. A process for the thermal conversion of petroleum hydrocarbonscomprising vacuum distilling a petroleum oil to form a heavy residuehaving a gravity of degrees API less than l0, a Conradson carbon residuenumber of at least 18, and a SUS viscosity at 210 F. of atY least 6,000,mixing the residue with a light catalytic cycle oil boiling in the rangeof approximately 400 to 650 F. to form a mixture having a ratio ofresidue to light catalytic cracked distillate fractions.

References Cited in the le of this patent UNITED STATES PATENTSv2,197,460 Adams Apr; 16, 1940 FOREIGN PATENTS 463,042 canada Feb. 7,1950 OTHER REFERENCES Sachanen: Chemical Constituents of Petroleum, page404, Reinhold Publishing Corporation, (1945).

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No..2,900,327 August 18, 1959 Harold Beuther It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should readascorrected below.

Column 6, line 58, for "gravitng" read gravity column '7, linel2, for"gravity of" read mgravity in m- Signed and sealed this lst day of March1960 (SEAL) Attest:

KARL H0 XLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

1. A PROCESS FOR THE THERMAL CONVERSION OF PETROLEUM HYDROCARBONSCOMPRISING VACUUM DISTILLING A PETROLEUM OIL TO FORM A HEAVY RESIDUE ASA BOTTOMS PRODUCT HAVING A GRAVITY IN *API OF LESS THAN 10, CONRADSONCARBON RESIDUE NUMBER OF AT LEAST 18, AND AN SUS VISCOSITY AT 210*F. OFAT LEAST 6000, MIXING THE RESIDUE WITH A LIGHT CATALYTIC CYCLE OILHAVING A BOILING RANGE OF APPROXIMATELY 400-650*F. TO FORM A MIXTUREHAVING A RATIO OF RESIDUE TO LIGHT CATALYTIC CYCLE OIL RANGING FROM 1:2TO 6:1, HEATING THE MIXTURE TO A TEMPERATURE OF 900 TO 1000*F. IN ASHORT PERIOD TO CARACK RESIDUE AND LIGHT CATALYTIC CYCLE OIL IN THEMIXTURE, SEPARATING THE CARACKED PRODUCTS INTO FUEL OIL AND VAPOR PHASE,FRACTIONATING THE VAPOR PHASE TO PRODUCE GASOLINE AND A RECYCLE OILHAVING A HIGHER BOILING RANGE THAN GASOLINE S SEPARATE FRACTIONS, ANDRETURNING RECYCLE OIL TO THE MIXTURE FOR HEATING TO CARACKINGTEMPERATURES.